Thread trimming mechanism for sewing machines

ABSTRACT

A thread trimming mechanism for sewing machines is provided which automatically cuts the thread with a pair of trimming knives secured to knive-mounting discs which move with a driving shaft rotating according to a predetermined action of a main shaft of the machine. The trimming knives engage the thread just under the eyelet-hole of the needle plate of the machine.

United States Patent Honda et a1.

[ THREAD TRIMMING MECHANISM FOR SEWING MACHINES [75] Inventors: l-lidemi Honda; Minoru Morita,

both of Wakayama, Japan [73] Assignee: Mitsubishi Electric Corporation,

Tokyo, Japan [22] Filed: Dec. 31, 1970 [21] App]. No.: 103,202

[52] U.S. Cl ..1 12/252 [51] Int. Cl. ..D05b 65/02 [58] Field of Search ..1 12/252 [56] References Cited UNITED STATES PATENTS 3,512,491 5/1970 Heimann et al. ..112/252 l [14 ml lllllfllllrlllllllm [451 Apr. 24, 1973 3,l41,432 7/1964 Reeber et a1. ..12/252 3.386.402 6/l968 Ross ..112/252 3,173,392 3/1965 Hedegaard ..112/252 Primary Examiner-James R. Boler Attorney0blon, Fisher, & Spivak 57 ABSTRACT 2 Claims, 21 Drawing Figures PATENIEDAPR 24 ms 'SHEET 0-105 11 30 3| 2 7| 28 l2 v 62 65 6424 22 56 30 63v INVENTOR. "muonu MORITA BY mm HONDA ATTORNEYS PATENTEDAPR24 wars 3.728.978 sum new 11 BL 7 N2.

PATENTEDAPR 24 I973 SHEET I U8UF 11 'Pmmmmzms 3,728,978 sum new 11 4 THREAD TRIMMING MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to thread trimming mechanisms for sewing machines, and more particularly, to a thread trimming mechanism for cutting thread just under the eyelet-hole of a needleplate in a sewing machine.

2. Background of the Invention In the past, immediately upon completing a normal sewing operation, it has been necessary to withdraw the cloth or material being sewn from the needle plate area of the machine and to trim the thread either by cutting the same with scissors or the like, or by pulling the thread over a knife-edged hook provided on the machine. The former method requires the use of an extra instrument, namely the scissors, and additionally is burdensome and inefficient in that extra maneuvering and hand manipulation of the cloth and the cutting means is required. The latter method, though it alleviates the use of scissors, still is not considered to be entirely satisfactory in that the material being sewn still must be withdrawn from the needle plate and maneuvered to the cutting edge, and furthermore, it is difficult to cut the thread sufficiently close to the material whereby, in many cases, it is still necessary to trim the same with scissors.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved thread trimming mechanism for use on a sewing machine which cuts thread close to the material and does not require manipulation of the material being sewn or the use of a separate cutting tool.

Another object of this invention is to provide a sewing machine wherein upper and lower threads can be cut when a signal is transmitted to a control means by a simple operation of an operator immediately after sewing the cloth to be treated or in the way of sewing it, which provides ends of thread as short as possible.

Still another object of this invention is to'provide a thread trimming mechanism for a sewing machine which cuts the thread from a piece of material being sewn at a point just below the eyelet-hole of the needleplate of the machine.

These and other objects are obtained in accordance with the present invention, which provides a thread trimming mechanism for sewing machines comprising a driving shaft rotating according to predetermined action of a main-shaft of the machine, first and second knife-mounting discs rotating in opposite directions to each other according to rotation of the driving shaft, and a pair of trimming knives secured to said knifemounting discs, respectively, the trimming-knives engaging with each other by means of rotation of said knife-mounting discs approximately just under the eyelet-hole ofa needle-plate to cut the thread.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate like or corresponding parts throughout the several views and in which:

FIG. 1 is a front elevational view illustrating a sewing machine in conjunction with the thread-trimming mechanism apparatus of the present invention;

FIG. 2 is a sectional view of the sewing machine shown in FIG. I wherein a part of the section is broken for clarifying the construction of the thread trimming mechanism;

FIG. 3 is a bottom view of the bed construction of the sewing machine shown in FIG. 2;

FIG. 4 is a left-end view of the machine shown in FIG. 1 being partially broken away for purposes of clarity;

FIG. 5 is a cross sectional view taken along line II of FIG. 2;

FIG. 6 and FIG. 7 are flat cross sections taken along the lines IIII of FIG. '5, respectively, FIG. 7 showing the state of an actuating member which has moved from the normal state shown in FIG. 6;

FIG. 8 is a cross sectional view taken along the line III-III of FIG. 6, showing the configuration of a cam constructed according to this invention;

FIG. 9 is an enlargement of a plan view showing the construction of trimming-knives and related structure, with the needle plate attached to the surface of the bed being removed for purposes of clarity;

FIG. 10 is a front view of FIG. 9;

FIG. 11 is a view showing the machine of this invention in operation, where the trimming-knives are engaging each other and cutting thread;

FIG. 12 is a front view showing the construction of the trimming-knives;

FIG. 13 is a schematic diagram, showing the operation of. driving members to actuate the trimmingknives;

FIG. 14 is a front sectional view showing the construction of a part for loosening the tension in the sewing machine of this invention;

FIG. 15 is a back view of FIG. 2, showing the inside construction, especially of a safety-keeping means formed according to this invention which is seen through a window provided at the back of an arm of the sewing machine;

FIG. 16 is a back view, showing only the construction of the safety-keeping means of FIG. 15;

FIG. 17 is a view showing actuation of the actuating member illustrated in FIG. 16;

FIG. 18 is a plan cross section taken along the line IVIV of FIG. 16;

FIG. 19 and FIG. 20 are side cross sections taken along the line V-V of FIG. 18 respectively; and

FIG. 21 is a front cross sectional view taken along the line VI-Vl of FIG. 5.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIG. I, the reference numeral 1 designates a bracket-arm and 2 represents a bed-plate of a sewing machine supported on a table 3. A needle-positioner clutch motor 4 attached to the undersurface of the table 3 has a pulley which is conventionally engaged with a balance wheel 5 of the machine through a belt for transmitting rotation of the motor to the machine so that the machine runs and drives the needle.

Preferably, the stop position of the needle-positioner clutch motor -4 is so arranged that generally, while an operator is treadling with a foot pedal 6 mounted on the table, the machine turns continuously at a high speed for driving the needle while, when the operator releases the pedal 6, the needle stops at its lowest position. Also, when the pedal 6 is treadled back in a given direction, or a signal is otherwise transmitted to the motor by the operation of another switch, the machine can be turned through only one revolution at a predetermined low speed so that a take-up may move from the lowest position of the needle to the highest position. As in the motors of most conventional sewing machines, a synchronizer 7 for detecting these positions is attached to the end of a main-shaft 8 in the bracket arm 1.

The main-shaft 8 is not axially movable, but is rotatably received within bearing-bushings 9, 10, and l 1, and substantially near its middle has a bevel gear 13 positioned thereon for driving a hook-shaft l2 and a vertical feed cam 14 and a horizontal feed cam 15 for feeding cloth, each of which cams is given amovement suitable for feeding cloth through engagement with respective driven members through rod connections.

The reference number 16 represents a needle bar which is axially supported by bearings so as to reciprocate upwardly and downwardly with respect to the rotation of the main-shaft 8 and at the top of the needle bar, a needle 17 is detachably mounted. A takeup mechanism 18 is operable in response to the reciprocation of the needle 17 for tensioning the thread as in conventional sewing machines. A pressure foot 19 is detachably secured to the lower end of a pressure bar 20 by a set-screw 21 and always is subject to the downward urging of a spring, not shown.

The hook shaft 12 is rotatably supported below the bed-plate 2 by a bushing 22 at one end and a stepped bearing-bushing 23 at its other end, axial movement being prevented by a collar 24 secured thereto. Rotation of the hook shaft 12 is at a speed twice that of the main-shaft 8, through the engagement of a bevel gear 26 on the lower end of a vertical shaft driven by the bevel gear 13 of the main shaft 8 which engages a gear on the upper end of shaft 25. The edge of the shaft 12 also has a conventional rotary hook 27 attached thereto.

A feed rock shaft 28 and a feed lifting rock' shaft 29 are each swingably supported on the bed-plate by spaced bushings 30. Also, these shafts are so arranged that they operate in the region of movement predetermined by the vertical feed cam 14 and the horizontal feed cam 15. On the feed rock shaft 28, a feed bar 32 is swingably mounted through an attaching arm 31 and on the feed bar a feed dog 33 is attached for feeding cloth of the work piece by an appearing and disappearing action of the feed dog from the groove for the feed dog of the needle plate 34, with cooperation of the feed rock shaft 28 and the feed lifting rock shaft 29, the same as in conventional sewing machines.

The reference numeral 35 represents a tension member which provides the suitable tensile strength to the thread by varying the biasing pressure of a tension spring 36, also in the same manner as that occurring in conventional machines. Other operations also will be performed in the same manner as in conventional sewing machines; that is, when a tension releasing lever 38 which is supported by a pin 37 at the lower end of the chin portion of the machine arm, has worked to the position shown in FIG. 4 by two-dots chain line, it presses a release pin 40, which is movably disposed in the hollow of a tension stud 39, and then presses a tension release washer 41 against the spring 36. Thereafter, with the pressure on a tension disc 42 by the spring 36 and washer 41 being relieved, as well as additive tensile strength toward the thread, it is possible to draw out the thread from a spool, as it is demanded.

The reference numeral 43 represents an oil pan which is releasably secured at the back of the bed, wherein lubricating oil to be supplied to each part of the machine is stored. The lubricant oil is supplied to each part by an oil-pump which acts according to the working of the machine.

In FIG. 8, there is shown a cam 45 for cutting thread, which is tightly secured to the main-shaft 8 by a setscrew 46 and is provided with a cam-groove formed as shown in FIG. 8. This configuration of the cam is suitable for cutting thread with knives after procuring the desired length of the upper and lower threads, as will be described hereinbelow. An actuating shaft 47 is rotatably and slidably supported on the wall of the machine-arm, as best clearly shown in FIG. 6. Tightly secured to the actuating shaft 47 by a set-screw is a cam follower 48. At the edge of the cam follower 48, there is rotatably attached a roller 49 which may engage with the hereinbefore-mentioned cam-groove of the cam 45. This roller 49 of the cam follower 48 is normally in a position having no cooperative relation with the cam, as shown in FIG. 6. However, in a manner to be described, when the actuating shaft 47 is actuated in the direction of an arrow A shown in FIG. 7, the roller 49 is displaced into the cam-groove and when the mainshaft 8 rotates slowly, as described before, the actuating shaft 47 is rotatably moved according to the configuration of the cam-groove.

Also secured to the actuating shaft 47 is a transmitting arm 51 which is connected to an arm of a driving shaft 52 by means of ball joints 53 and a rod 54, so that when the actuating shaft 47 works with the cam 45, the movement thereof is transmitted to the driving shaft 52 supported by the bed-plate 2, as shown best in FIG. 5. A lever 56 which is pressed into a boss in the middle of the machine arm, as shown in FIGS. 2, 5, and 21, also is pivotally supported on a shaft 58 secured to the bracket arm 1 by a set-screw 57, a fork portion 59 at the upper part of the lever being in the form of a semi-circle and fitting into the gap between collars 61 attached to the actuating shaft 47 by pins 50, and the lower part of the lever 56 being connected to a link 62 by a rivet and always pressed against one side thereof by a spring 63.

Referring now to FIG. 21, a pasted-type solenoid 64 is attached to the bed 2. When a predetermined voltage is conducted to this solenoid, according to the action of an electromagnet, a piston 65 is forced out in the direction of the arrow, and the lever 56 is thereby actuated by the pulling of the link 62 connected to the edge thereof, whereby the actuating shaft 47 moves from the position shown in FIG. 6 to the position shown in FIG. 7. Thus, the roller 49 which ordinarily does not engage the cam 45 comes into engagement with the camgroove so that the actuating shaft 47 may be turned ac cording to the cam configuration and led by the rotation of the main-shaft 8.

The reference numeral 52 represents a driving shaft as mentioned before, which is rotatably supported in the bed plate 2. At one edge portion, protruding in the side of the rotary hook on shaft 12, a driving-crank 66 is tightly secured by a set-screw, as shown in FIG. 3 and FIG. 12. A pair of knife-mounting discs 67 and 68 are each turnably fitted about the stepped portion of the bearing-bushing 23 which receives the hook shaft 12, as shown in FIG. 2, which is prevented from being axially moved by a collar 69 of the bearing-bushing and the wall of the bed-plate. A boss 70 mounted at the knife-mounting disc 68 and the longer arm portion of the driving crank 66 are connected to each other by a link 71. A groove 72 formed in the knife-mounting disc 67 engages with a block 73 mounted at another arm portion of the driving crank 66. Thus, when the actuating shaft 52 moves in the direction of an arrow C shown in FIG. 12, the knife-mounting disc 67 turns through a relatively small angle in the direction of an arrow A on the bearing-bushing 23, and the knife-mounting disc 68 turns through a larger angle in the direction of an arrow B, by movement respectively of the link 71 connected thereto in a downward, or counterclockwise, direction and movement of the block 73 and the groove 72. In this case, as clearly shown in the diagram of FIG. 13, the knife-mounting disc 67 is so designed that it moves with very small rotation-angle 0 with regard to the actuation angle a of the knife-mounting disc 68.

The reference numerals 74 and 75 represent the trimming-knives having sharp cutting edges at their front portions. The knife 74 is attached by a set-screw 93 to the knife-mounting disc 67, and the trimming knife 75 is attached by a set-screw 94 to the knifemounting disc 68, along with a thread-guide 76, to be described hereinbelow, as shown in FIGS. 10, l1, and 12, each being adjustably mounted in its respective position.

As described above, when each of the knife-mounting discs 67 and 68 turns in the respective desired direction so that the knives mounted thereon bite each other, as shown in FIG. 11, immediately under the eyelet-hole 77 of the needle plate 34, then the upper thread 78 and the lower thread 79 extending from the bobbin case of the rotary hook are cut through and it is so designed that the length of the lower thread remaining at the cloth after being cut is as short as possible.

As clearly shown in FIG. 10, the movement of the knife-mounting disc 67 is made as small as possible so that the knife 74 may be retracted in the region where it does not touch with the feed dog 33, acting so as to come from and go into the needle plate and that it may move to the position just under the eyelet-hole 77 of being treated are distinguished from the upper thread 80 between the rotary hook and the needle, which should not be cut and which, extending from the side of the needle 17, travels the outer periphery of the rotary hook, and then, as it rotatably proceeds from the position shown in FIG. 10 to that in FIG. 11, the upper thread 78 and the lower thread 79 are thrown to a hook 81 and are pulled out by the desired length from the spool and the bobbin case, respectively.

Also, at the time that the thread guide 76 rotates to pull out the upper thread from the spool, the lever 56 is pivoted by the piston 65 of the solenoid 64 and the interconnection link 62 so that the roller 49 of the cam follower 48 moves into and engages the cam groove, and the bell-crank 83 connected by a wire 82 passing through an elongate protective tube is secured to the lever 56 at one side thereof so that the tension releasing lever 38 is operated through a coupling rod 82 between the lever 38 and the bell crank 83. Since the resiliency of the spring 36 in the tension member 35 is relieved by operation of the release pin 40 and the tension release washer 41, whereby charge pressure of the tension disc 42 is released, there is no additive tensile strength toward the upper thread by the tension, and so it is of course possible to take out the upper thread from the spool, as desired.

Thus, the upper and lower threads are taken out by the thread-guide 76 before they are cut through, so that the upper thread may not incidentally get out of the eye ofthe needle 17, on the sewing cycle after trimming the thread.

Referring especially now to FIGS. 16 and 17, the reference numeral 83 represents a collar which is secured to the main-shaft 8 by a set-screw 85 and engages with an end face of the bearing 10 forpreventing the same from moving axially with regard to the mainshaft. Particularly of interest is a flanged part 86 of the collar 84 being provided at the peripheral face with a notch 23a.

The reference numeral 87 represents a stopper which is secured by a rivet 88 to the lever 56. The stopper engages with the flange 86 of the main-shaft collar 84 for positioning the lever 56. In other words, during the machine running, when the operator releases the operation of the foot-pedal, the machine stops in the manner that the needle bar is necessarily in the lowest position by means of the action of the needle-positioner clutch motor. The stopper 87 in that time has such a relation with the flange 86 of collar 84 that the stopper 87 may freely move without being interrupted by the flange 86. If a suitable switch is operated by an operator, however, so that the solenoid 64 is energized through the control means for the motor whereby the piston 65 of the solenoid may pull the link 62 in the direction of an arrow shown in FIG. 21 by means of an attractive force of the electromagnet, so as to actuate the lever 56 and to axially displace the actuating shaft 47, then when the roller 49 and the cam completely engage with each other, a switch, not shown, may be suitably provided for being changed by the actuating shaft 47 to actuate the relay in the control box. The needle-positioner clutch motor 4 with very low speed then rotates the main-shaft 8 with correction in one rotation of the machine, about 230 rotating angle, until the needle bar moves from its lowest position and the take-up reaches its highest position. During that correctional rotation, the stopper 87 which has moved to the position shown in FIG. 18 by the twodotted chain line, can no longer return to the original position due to the interruption of the flange portion 86 of the main-shaft collar 84. This is because the roller 49 engages with the cam 45 by means of suitable switch operation for cutting the thread and immediately after the rotation for start, the switch operation is released, thereby de-energizing the solenoid 64, but even so, since the stopper 87 is being interrupted by the collar flange 86, the lever 56 cannot be returned to the original position under the influence of the spring 63, and the position of the lever 56 is thus maintained as well as in the engagement of the roller and the cam until the complete thread-trimming is accomplished.

Further, while the take-up 18 moves to its highest position and the main-shaft is rotated with correction of the position at low speed in one rotation by the needle-position clutch motor, as described before, the thread-guide 76 is rotated by the trimming cam 45 alongwith the knife-mounting disc 68 to pull out the desired length of thread before the thread is cut by engagement of the knives. When the trimming is finished, the correctional rotation of the main-shaft stops and the relative position between the stopper 87 and the collar 86 is in the approximate state as shown in FIG. 19, whereby the stopper again freely works without any interruption by the collar. Also, when the correctional rotation stops, the energization of the solenoid 64 is automatically cut off, and so the lever 56 returns to the original position under the force of the spring 63. Then, of course, the roller 49 of the cam follower 48 disengages from the trimming cam 45 and there is no longer any working relation between the cam and the roller.

According to this invention, after the workpiece cloth is sewed up to the predetermined position, for the purpose of removing the workpiece from the machine and trimming the thread, the operator need only to release the treadle-operation of the foot-pedal to stop the machine at the lowest position of the needle by automatic control of the needle-positioner clutch motor, then through operation of the trimming-switch, any suitable voltage is conducted to the solenoid 64 for actuating the lever 56 to cause the roller 49 and the trimming-cam 45 to engage with each other. A signal is then transmitted to the needle-positioner clutch motor and the main-shaft 8 of the machine is rotated within one rotation so that the take-up exists in the highest position. The driving crank 66 is rotated by the trimming-cam through the ball-joints 53 and shaft 52. Each of the knife-mounting discs 67 and 68 is actuated by the driving crank 66. Then only the desired length of the upper thread and the lower thread is pulled out by the thread-guide 76, and the cutting of such thread is permitted. Since each of the trimming knives engages with the other to cut through the thread under the eyelet-hole of the needle-plate as close to the workpiece cloth as is possible, the ends of the thread is made very short.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teaching. it should therefore be understood that within the scope of the appended Claims, the invention may be practiced otherwise than as specifically described herein.

What IS claimed as new and desired to be secured by Letters Patent of the United States is:

1. A thread-trimming mechanism for machines, which comprises:

a cam mounted to a main-shaft of the machine;

an actuating shaft having a cam-follower thereon being engagable and disengagable with said cam upon movement of said actuating shaft;

means for selectively moving said actuating shaft for causing engagement between said cam and said cam-follower;

cooperable engaging thread trimming knives and linkage connecting the same to said actuating shaft for actuating said knives upon engagement of said cam and said cam-follower through rotation of said actuating shaft by said main-shaft;

means for retaining the engagement of said cam and cam-follower until said thread-trimming knives complete the cutting of said thread;

said thread-trimming knives being disposed just below the eyelet-hole of the machine needle-plate for cutting the thread as closely as possible to the workpiece cloth.

2. A thread-trimming mechanism for machines which comprises:

a driving shaft connectable to a main-shaft of the machine through a cam mounted on said mainshaft, an actuator shaft having a cam-follower engageable and disengageable with said cam, and means for selectively moving said actuating shaft to cause engagement between said cam and said cam-follower for selectively rotating said driving shaft with said main shaft;

first and second knife-mounting discs coaxially mounted and being connected to said driving shaft for rotation in opposite directions upon rotation of said driving shaft;

a pair of thread trimming knives adjustably secured to said knife-mounting discs, respectively, said trimming knives being engageable with each other through rotation of said knife-mounting discs approximately just below the eyelet-hole of a needleplate of said machine to cut the thread;

thread-guide means adjustably secured on one of said first and second knife-mounting discs and being rotatable therewith, through which a predetermined length of the lower thread from a bobbin case and that of the upper thread from a spool may be pulled out before the trimming knives engage for cutting the same;

means for normally maintaining the upper thread under a predetermined tension;

means for relieving the tension on the upper thread when said thread-guide means is rotated to pull out the upper thread from the spool; and

means for maintaining said driving shaft connected to said main-shaft of the machine by retaining the engagement of said cam and said cam-follower until said thread-trimming knives complete the cutting of said thread.

sewing sewing 

1. A thread-trimming mechanism for sewing machines, which comprises: a cam mounted to a main-shaft of the machine; an actuating shaft having a cam-follower thereon being engagable and disengagable with said cam upon movement of said actuating shaft; means for selectively moving said actuating shaft for causing engagement between said cam and said cam-follower; cooperable engaging thread trimming knives and linkage connecting the same to said actuating shaft for actuating said knives upon engagement of said cam and said cam-follower through rotation of said actuating shaft by said main-shaft; means for retaining the engagement of said cam and cam-follower until said thread-trimming knives complete the cutting of said thread; said thread-trimming knives being disposed just below the eyelet-hole of the machine needle-plate for cutting the thread as closely as possible to the workpiece cloth.
 2. A thread-trimming mechanism for sewing machines which comprises: a driving shaft connectable to a main-shaft of the machine through a cam mounted on said main-shaft, an actuator shaft having a cam-follower engageable and disengageable with said cam, and means for selectively moving said actuating shaft to cause engagement between said cam and said cam-follower for selectively rotating said driving shaft with said main shaft; first and second knife-mounting discs coaxially mounted and being connected to said driving shaft for rotation in opposite directions upon rotation of said driving shaft; a pair of thread trimming knives adjustably secured to said knife-mounting discs, respectively, said trimming knives being engageable with each other through rotation of said knife-mounting discs approximately just below the eyelet-hole of a needle-plate of said machine to cut the thread; thread-guide means adjustably secured on one of said first and second knife-mounting discs and being rotatable therewith, through which a predetermined length of the lower thread from a bobbin case and that of the upper thread from a spool may be pulled out before the trimming knives engage for cutting the same; means for normally maintaining the upper thread under a predetermined tension; means for relieving the tension on the upper thread when said thread-guide means is rotated to pull out the upper thread from the spool; and means for maintaining said driving shaft connected to said main-shaft of the machine by retaining the engagement of said cam and said cam-follower until said thread-trimming knives complete the cutting of said thread. 